Getting better at integrating mallees in farms

Adding nutrients to belts of mallee trees integrated into paddocks with pasture or crops can significantly increase mallee growth, according to the latest research from the Future Farm Industries Cooperative Research Centre’s Woody Crops Program.

The CRC’s Woody Crops Program leader, Paul Turnbull, said that in some ways that shouldn’t be surprising.

“We all know that generally speaking, if you add nutrients to plants, they’ll grow better,” Turnbull said. “But we thought that when belts of mallees were growing in paddocks, water was most likely the major limiting factor. Our latest research has proven that is not necessarily the case and that nutrients, especially nitrogen, are very important.”

The research, which was supported by the Australian Government’s Second Generation Biofuels Research and Development Program Fund (Gen2 Program), sought to learn how to plant mallees into farming landscapes in a way that optimised the integration of trees and crops. Another surprising finding was that building bunds or small dam walls below the trees capture water and nutrients and the trees grow better.

“It’s one thing to know that something like bunds may help, but it is another thing entirely to know exactly how and where they should be built in a farm system and just how much difference they will make,” Turnbull said.

“Answers to these sorts of questions enable us to really refine our recommendations as to how farmers can integrate belts of mallee trees into their farms and we can quantify the benefits of different approaches and management options.”

Mallee trees are a potential source of biomass for the developing biofuels industry. There is strong motivation for the development of biofuels as they will reduce reliance on fossil fuels, reduce greenhouse gas emissions in the transport sector and, providing production costs are competitive, may mean lower fuel prices in the long term by increasing the supply of transport fuels.

The CRC’s biofuel research focuses on mallee trees, which are a good source of biomass for biofuel production. When integrated into wheatbelt farms, mallees have the potential to diversify farm income and return significant natural resource management benefits, while minimising disruption to food production.

“The integration of mallees into wheatbelt farms has now been studied for over 20 years and has been successfully demonstrated on over 1000 farms in Western Australia.

“The research we have just completed has used highly sophisticated equipment and complex modelling to produce data and recommendations that will truly make a difference to farmers who want to grow mallees,” Turnbull said.

“The modelling and data collection in this project shows that by increasing the distance between the rows of trees from two metres to 15 metres and by considering biomass growth and the competition with adjoining crops, the cost of biomass is reduced by 12% and overall farm profits from biomass and grain are maximised.

“We have also quantified the likely effects of the mallee trees on the crop that grows between the mallee belts. From this we know exactly how close to the trees crops can be planted in different seasonal conditions.”

Turnbull said there was still more research to do but results to date have proven that mallee belts integrated into crops could be a sustainable and profitable option for wheatbelt farmers.

“The interest shown by the aviation industry in mallee biofuel is fostered by this important work and helps farmers and biofuel plant operators work out a reasonable price for biomass supply. What is really pleasing about this work is that benefits flow to farmers and transport fuel consumers while improving regional communities and the environment.”